Stair Widths

project planning & design
1

Can I get some clarification regarding the differences between 1) min. stair width of 36" under 50 occupancy/ 44" 50+ occupancy AND 2) min. width of 48" between handrails?

  1. is measured to the outside of the stair and handrails can project 4-1/2" into that space on both sides?
  2. is for Accessible Egress only? So there are a certain number of stairs in a building that need to meet this requirement and the rest of the stairs in the building need to meet option 1?

Also in regards to “only 30” of a stair from a handrail counts toward the egress requirement". So, for an occupant load of 480 x 0.3 = 144 divided by 2 egress stairs (under 500 occupancy) = 72" per stair. but only 60" of that counts because of 30" from each handrail? So how do you account for the missing 12" required for egress?

2

Hi @Tshwayder - there are a lot of variables here but in general, this is a case where you must use the most stringent requirement so that you meet all requirements of the building code.

If your occupant load only requires a 36" stair width, but your project doesn’t meet the exceptions listed in IBC 1009.3.2, then a 48" wide staircase between handrails is required.

In your second example (IBC 1014.9) you just need to provide an intermediate handrail along the center of the stairs. This is done often on wide staircases.